Catheters for delivery of material, generally fluids, into anatomical systems such as the vascular system are known in the art. Such catheters generally include an elongated catheter body with a sidewall which defines a catheter lumen. The catheter lumen has one end, referred to as the proximal end, through which fluid is introduced into the catheter lumen and another end, referred to as the distal end, from which fluid exits from the catheter lumen. One catheter design uses a single catheter lumen which is inserted into the anatomical system with the aid of a guidewire which passes through the lumen.
Fluid introduced into the proximal end of the catheter is generally passed through the lumen of the catheter under pressure supplied at or near the proximal end. The fluid then leaves the catheter through ports generally disposed at or near the distal end of the catheter. Such ports may include a hole at the end of the distal portion of the catheter. Various designs known in the art include one or more holes through the sidewall of the catheter, such as catheters by Mewissen (Meditech), EDM (Referral Systems Group), and the various MacNamara catheter systems, all of which are referenced in Diagnostic Imaging, Nov. 1, 1991. A catheter referred to in "Pulse-Spray Pharmacomechanical Thrombolysis," J. J. Bookstein and K. Valji, Cardiovascular and Interventional Radiology, v. 14, pp. 352-54 ("Bookstein"), has exit slits spaced along its distal end to perform pulse-spray pharmacomechanical thrombolysis. Bookstein emphasizes use of high-pressure pulses of brief duration to optimize thrombolysis procedures using urokinase as the fibrinolytic agent. Bookstein further describes using pulse-sprays from sidewall slits to perform angiography, and to perform thrombolysis on dialysis grafts.
U.S. Pat. Nos. 5,250,034 and 5,267,979 to Appling et al disclose side-slit catheters wherein the slits are configured to serve as pressure responsive valves, thereby resisting back flow of fluid into the catheter through the slits.
Although these two patent references, as well as the other above cited references, disclose various patterns and configurations of apertures in the sidewalls of catheters, in all of these references the fluid exits the catheter lumen generally orthogonally with respect to the longitudinal axis of the catheter lumen. For this and for various other reasons, current catheters suffer from various disadvantages and drawbacks when used to introduce fluids into anatomical systems, such as the vascular system. For example, when used to perform thrombolysis, fluid must be introduced at or near the thrombus to minimize the risk of clot fragmentation that can result in distal embolization occurring prior to effective clearing of the initial occlusion. Such clot fragmentation may result in tandem lesions, which may further restrict blood supply to the affected body part of the patient or cause other undesirable complications. The prior art has attempted to address these risks by increasing the pressure or exit force of the fluid from the side holes of the catheter, by increasing the number or varying the size of the side holes in the catheter, or both.
In addition, because of the invasive nature of using catheters to introduce fluid into the vascular system, such as in performing thrombolysis of a blood vessel, it is desirable to shorten the time needed to effectively introduce the desired fluid. In particular, the amount of time required to lyse a thrombus is preferably kept to a minimum. To minimize the time needed for lysing a thrombus or for performing any other procedure involving introduction of fluid through a catheter, it is necessary for the fluid to be accurately and efficiently introduced at the desired location in the vascular system. In the context of thrombolysis, for example, the lytic agent needs to be dispersed within the blood vessel in such a way that it acts to effectively dissolve the clot in a minimum amount of time. The catheters and associated procedures of the prior art need to be improved to more optimally place and disperse fluid, such as lyric agents, in the zone of interest within the patient's vascular system.
Thus, there is a need for an improved catheter which introduces fluid into the vascular system in a manner which increases the efficacy of the fluid being introduced, thereby minimizing both the amount of fluid needed to perform the desired procedure, as well as the time required for effectively completing such procedure.